The Information Technology Infrastructure Library (ITIL) (a trademark of the British government) is a collection of best practices for implementing IT service management. The focus of the ITIL is on service supports and service delivery. One of the service supports is configuration management. Configuration management is a process of identifying configuration items (CI) subjected to IT service management and maintaining, updating, verifying, and auditing information regarding the configuration items. Configuration items are resources subjected to configuration management. Configuration items include not only system resources including hardware and software but also facilities necessary to provide IT services, rule books regarding the operations of IT services, documents such as operating procedure manuals and block diagrams, services for maintenance information, processes, human resources, and the like. In the ITIL framework, it is recommended to centrally manage configuration items using a configuration management database (CMDB). A CMDB is a database in which at least one predetermined attribute of each configuration item and relations with other configuration items are recorded. Capabilities provided by incorporating the CMDB include the capability to automatically discover information on configuration items (also called discovery or automatic detection) and the capability of automatically updating information on configuration items (also called tracking).